Hydrogen peroxide as a signal mediator at inducing heat resistance in wheat seedlings by putrescine

Polyamines are multifunctional stress metabolites of plants. However, information on the effect of exo­genous polyamines on plant resistance to high temperatures is contradictory, and it remains unclear which signal mediators are involved in the realization of their physiological effects. The possible involvement of hydrogen peroxide as a mediator under the action of exogenous diamine putrescine on the resistance of etiolated wheat seedlings (Triticum aestivum L.) to hyperthermia (10-minute heating at 46°C) and the functioning of antioxidant system was investigated. It was established that the treatment of seedlings with putrescine in 0.25–2.5 mM concentrations caused a significant increase in their heat resistance. In response to the putrescine effect, a transient increase in the H2O2 content occurred in the root cells. This effect was eliminated by treatment of seedlings with a diamine oxidase inhibitor aminoguanidine and an NADPH oxidase inhibitor imidazole. These inhibitors, as well as the scavenger of hydrogen peroxide dimethylthiourea (DMTU), mitigated the effects of increased heat resistance of seedlings and increased activity of superoxide dismutase and catalase caused by putrescine. Under the influence of DMTU and imidazole, but not aminoguanidine, the effect of increasing the activity of guaiacol peroxidase in the roots of seedlings treated with putrescine was eliminated. The conclusion was made about the role of hydrogen peroxide and the possible participation of diamine oxidase and NADPH oxidase in its formation during the implementation of the stress-protective effect of putrescine on wheat seedlings

Phenylalanine ammonia-lyase activity and content of flavonoid compounds in wheat seedlings at the action of hypothermia and hydrogen sulfide donor

At present hydrogen sulfide (H2S) is considered as one of the signal mediators in plant cells. However, its role in formation of plant resistance to low temperatures and, in particular, in regulation of secondary metabolism under stress conditions remains poorly understood. The influence of H2S donor sodium hydrosulfide (NaHS) on phenylalanine ammonia-lyase (PAL) activity and content of flavonoids in wheat seedlings at normal temperature (21 °C) and under cold hardening conditions (7 days at 3 °C) was studied. After 2 days of the hardening temperature, a transient increase in PAL activity was noted. Also, activity of the enzyme was increased by treatment of plants with 0.1 or 0.5 mM NaHS under normal temperature conditions and especially at the background of cold hardening. By themselves, the cold hardening and the action of H2S donor caused an increase in total content of flavonoids and amount of anthocyanins. With the combination of hypothermia and treatment of seedlings with NaHS, this effect enlarged and the total content of flavonoids increased by 3.8, and anthocyanins increased by 1.8 times in comparison to the control. Treatment with the H2S donor caused a decrease in content of the lipid peroxidation product malonic dialdehyde in seedlings after the action of hardening temperature, and especially after their freezing at –5 °C. Also, under the influence of NaHS, survival of hardened and unhardened seedlings after cryostress increased. It was concluded that one of the mechanisms of the positive influence of the H2S donor on resistance of wheat seedlings to hypothermia is the PAL-dependent accumulation of flavonoid compounds, which have a high antioxidant activity, and a decrease in effects of secondary oxidative stress

ИНДУЦИРОВАНИЕ СОЛЕУСТОЙЧИВОСТИ 24-ЭПИБРАССИНОЛИДОМ ПРОРОСТКОВ ПРОСА (Panicum miliaceum) С УЧАСТИЕМ АКТИВНЫХ ФОРМ КИСЛОРОДА

The treatment of millet seedlings with 24-epibrassinolide (24-EBL) was shown to cause a transient increase in their hydrogen peroxide content, the subsequent activation of antioxidant enzymes (superoxide dismutase, catalase, guaiacol peroxidase) and the development of their resistance to salt stress. Antioxidant dimethylthiourea and NADPH oxidase inhibitor imidazole leveled these processes. It was concluded that the induction of millet salt tolerance by exogenous 24-EBL was mediated by the enhancement of reactive oxygen species level associated with the increased activity of NADPH oxidase.Показано, что обработка проростков проса 24-эпибрассинолидом (24-ЭБЛ) вызывала транзиторное увеличение в них содержания пероксида водорода, последующую активацию антиоксидантных ферментов (супероксиддисмутазы, каталазы, гваяколпероксидазы) и развитие устойчивости к солевому стрессу. Антиоксидант диметилтиомочевина и ингибитор НАДФН-оксидазы имидазол нивелировали эти процессы. Сделано заключение, что индуцирование солеустойчивости проса экзогенным 24-ЭБЛ опосредовано усилением генерации активных форм кислорода, связанным с повышением активности НАДФН-оксидазы

Signal mediators at induction of heat resistance of wheat plantlets by short-term heating

The effects of functional interplay of calcium ions, reactive oxygen species (ROS) and nitric oxide (NO) in the cells of wheat plantlets roots (Triticum aestivum L.) at the induction of their heat resistance by a short-term influence of hyperthermia (heating at the temperature of 42 °С during 1 minute) have been investigated. The transitional increase of NO and H2O2 content, invoked by heating, was suppressed by the treatment of plantlets with the antagonists of calcium EGTA (chelator of exocellular calcium), lanthanum chloride (blocker of calcium channels of various types) and neomycin (inhibitor of phosphatidylinositol-dependent phospholipase C). The rise of hydrogen peroxide content, caused by hardening, was partially suppressed by the action of inhibitors of nitrate reductase (sodium wolframate) and NO-synthase (NG-nitro-L-arginine methyl ester – L-NAME), and the increasing of nitric oxide content was suppressed by the treatment of plants with the antioxidant ionol and with the scavenger of hydrogen peroxide (dimethylthiourea). These compounds and antagonists of calcium also partially removed the effect of the rise of plantlets’ heat resistance, invoked by hardening heating. The conclusion on calcium’s role in the activation of enzymatic systems, generating reactive oxygen species and nitric oxide, and on the functional interplay of these signal mediators at the induction of heat resistance of plantlets by hardening heating is made

State of antioxidant system in triticale seedlings at cold hardening of varieties of different frost resistance

Efect of cold hardening on state of antioxidant system (AOS) of triticale (×Triticosecale Wittmack) seedlings of varieties, difered in frost resistance, namely Buket and Raritet (winter, high-frost-resistant), and Alexandra and Pidzymok Kharkovskiy (facultative, less resistant) was studied. In absence of cold hardening, a clear connection between studied indicators of the AOS state and frost resistance of the varieties was not observed. After hardening of seedlings at 2–4 °C for 6 days, the activity of superoxide dismutase (SOD) and catalase increased in the high-frost-resistant varieties Buket and Raritet. In less resistant ones—Alexandra and Pidzymok Kharkovskiy—the activity of these enzymes changed less signifcantly. At the same time, the activity of guaiacol peroxidase increased more noticeably after hardening in these varieties. Hardened seedlings of the Buket, Raritet and Alexandra varieties had signifcantly higher sugar content than the Pidzymok Kharkovskiy. The proline content in response to cold hardening increased in all varieties, while the absolute values in the varieties Buket, Raritet and Pidzymok Kharkovskiy were signifcantly higher than in the Alexandra. Cold hardening caused a signifcant increase in the content of anthocyanins and favonoids, absorbing in UV-B, in the Buket, Raritet and Alexandra, but not in the Pidzymok Kharkovskiy. The content of lipid peroxidation product malondialdehyde after a 6-h damaging action of −7 °C increased in the varieties Alexandra and Pidzymok Kharkovskiy and slightly changed in the Buket and Raritet. In general, a positive relationship was found between AOS activity and frost resistance of hardened triticale seedlings. This relationship was most clearly manifested for indicators of SOD activity and favonoid content

Role of Ca ions in the induction of heat-resistance of wheat coleoptiles by brassinosteroids

The involvement of Ca2+ into the signal transduction of exogenous brassinosteroids (BS) (24-epibrassinolide – 24-EBL and 24-epicastasterone – 24 ECS) causing the increase of heat resistance of the cells of wheat (Triticum aestivum L.) coleoptiles was investigated using calcium chelator EGTA and inhibitor of phosphatidylinositol-specific phospholipase C – neomycin. Twenty-four-hour treatment of coleoptile segments with 10 nM solutions of 24-EBL and 24-ECS led to a transient increase in the generation of superoxide anion radical by cell surface and the subsequent activation of superoxide dismutase and catalase. Pretreatment of coleoptiles with EGTA and neomycin depressed to a considerable extent these effects and leveled the increase in heat resistance of wheat coleoptiles that were caused by BS. Possible mechanisms of involvement of calcium signaling into the formation of reactive oxygen species in plant cells and induction of heat resistance of plant cells by the action of exogenous BS have been discussed